The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
The advent of Ethernet as a Metropolitan and Wide-Area Networking technology imposes a new set of Operations, Administration and Maintenance (OAM) requirements on Ethernet's traditionally Enterprise-centric modus operandi. The expansion of this technology into the domain of Service Providers, where networks are substantially larger and more complex (compared to Enterprise) and user-base is wider, makes the notion of operational management of link uptime crucial. More importantly, the absolute timeliness in isolating and responding to a failure becomes mandatory for normal day-to-day operations, and OAM translates directly to the competitiveness of the Service Provider.
In computer networks such as the Internet, frames are sent from a source to a destination via a network of elements including links (communication paths such as telephone or optical lines) and nodes (for example, bridges directing the frame along one or more of a plurality of links connected to it) according to one of various routing protocols. Network segments may include bridged networks where no assumptions are made about where in the network a particular device is located and frames are forwarded between devices through a process known as MAC Address learning.
Bridged networks may, however, include forwarding loops which may result in flooding of the network. In order to avoid loops, protocols, such as the Spanning Tree Protocol (STP), ensure a loop free active topology for a bridged network. STP allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links.
The STP creates a tree of connected OSI layer-2 bridges or nodes (e.g., Ethernet switches), and disables the links which are not part of that tree, leaving a single active path between any two network bridges. Further, the STP may rely on a routing algorithm resident at each node that computes the spanning tree based on lowest total cost of the costs associated with each link traversed on a data path. Specifically, the algorithm may determine the root node within a bridged network and compute the port roles (root, forwarding, or blocked) to forward data to the root node. Information regarding node IDs and root path costs may be exchanged using special data frames called Bridge Protocol Data Units (BPDUs). Based on periodic BPDUs updates (e.g., every two seconds), nodes may keep track of network changes and start and stop forwarding at ports as needed.
In some instances, a node may be misconfigured, fail, experience a hardware fault or software error, or otherwise behave incorrectly causing the loop free topology or elements implementing the loop free protocol algorithm to fail. Node failure or malfunction within a loop free topology can give rise to a loss of connectivity between two or more nodes. Ethernet OAM protocols allow a user to detect connectivity problems using built in fault isolation functions, however they do not allow reliable identification of the underlying location and cause of all types of network problems. Particularly, if any spanning tree instances fail, the troubleshooting process becomes complex (e.g., due to loops, blocking of management interfaces, unreachable devices, etc.) Accordingly, when a loss of connectivity is determined, a manual inspection, node by node, is generally made by a network administrator, a processor, or other user to determine which nodes have failed or malfunctioned. However, a node by node manual inspection of each of the nodes in a bridged network may be time-consuming and/or error prone.